Gaseous mixing device for regenerator heaters

ABSTRACT

A gaseous mixing device for heaters for blast furnace stoves and the like characterized in that the mixing device is formed entirely from refractory materials and is constructed so as to impart a swirling or rotational movement to a mixture of air and combustible gas to thoroughly admix the same before it is introduced into a combustion chamber.

[ 1 Dec. 18, 1973 Junkermann 431/173 X Clarkson...............

ABSTRACT 4' Claims, 4 Drawing Figures l I III! I O United States Patent [191 Rossow GASEOUS MIXING DEVICE FOR REGENERATOR HEATERS [75] Inventor: Rolf Rossow, Bochum, Germany [73] Assignee: Dr. C. Otto & Comp. SmbH,

Bochum, Germany [22] Filed: Sept. 27, 1971 [21] Appl. No.: 184,042

[30] Foreign Application Priority Data Sept. 26, 1970 Germany... P 20 47 453.7

[52] US. 431/173, 431/174, 431/185, 432/222 [51] Int. Cl. F23c 5/18 [58] Field of Search....................... 431/9, 173, 174, 431/185, 353; 263/19 R [56] References Cited UNITED STATES PATENTS 11/1956 Simmons....,.................... 431/173 X WENIEDMB 18 ms BIFTSBSO INVENTOR. ROLF ROSSOW w MZZaW ATTORNEYS GASEOUS MIXING DEVICE FOR REGENERATOR HEATERS BACKGROUND OF THE INVENTION There are efforts in the steel industry to increase the temperature of the air blast fed to a blast furnace to the range of about 1,200 to l,300C (i.e., 2,l92 to 2,372F). However, in order to obtain such temperatures, the heater itself must be heated to a temperature of about 1,500C (2,732F) or to even higher temperatures. In a blast furnace stove, for example, the combustion chamber is normally a vertical passageway in which blast furnace gas is burned extending from a point at the bottom of the stove to the bottom of the dome and through which the hot products of combustion pass upwardly to the dome and thereafter pass downwardly through brick checkerwork. The burner at the bottom of the combustion chamber, which introduces a mixture of air and gas into the combustion chamber, is normally formed from metal; however the durability of such metallic burners is substantially reduced as the temperatures are increased to the desired values. In addition, it is necessary for the protection of the metallic burners to provide special measures such as, for example, the provision of water cooled valves and similar devices. Such burners not only increase the susceptibility of the device to operational failures but also are quite expensive.

Furthermore, to obtain such high temperatures in a combustion chamber for a blast furnace stove, blast furnace gas is no longer sufficient. That is, it is necessary to increase the caloric capacity of the gas by admixture of coke oven gas or natural gas with the blast furnace gas.

Because of the reduced durability of metallic burners at higher temperatures and because of the use of a gas mixture consisting of blast furnace gas and a gas of high caloric value, prior art burners cannot be used for the heating of air heaters (e.g., blast furnace stoves) operated at said high temperatures or, at least, are not economical.

SUMMARY OF THE INVENTION In accordance with the present invention, a refractory gaseous mixing device (i.e., burner) for air heaters such as blast furnace stoves is provided which does not have the disadvantages of metallic burners of the prior art. That is, the burner must be able to withstand the adverse conditions caused by the higher temperatures.

With this objective in view, the present invention resides in the provision of a refractory burner for an air heater including a combustion chamber, a substantially cylindrical mixing chamber extending axially downwardly from the lower end of the combustion chamber and fonned from refractory material, and at least one horizontally-extending gaseous fuel and air admission channel formed from refractory material leading tangentially into the cylindrical mixing chamber for admitting gaseous fuel and air to the mixing chamber.

In accordance with one embodiment of the invention, there are provided two or more horizontallyextending channels, the channels being superimposed and serving alternately as fuel gas and admission channels. According to another embodiment of the invention, there are three superimposed channels of which the intermediate channel serves for the admission of air and the upper and lower channels for the admission of gaseous fuel to the mixing chamber. At the point where the channels intercept the mixing chamber, they have a substantially rectangular cross section, each of the same width. According to still another embodiment of the invention, the mixing chamber is formed to have at its upper end a comically-shaped throat.

The construction of the burner from refractory materials, especially from firebrick, provides a burner arrangement which is insensitive to influences caused by the high operating temperatures. The introduction of the fuel gas and air streams into the mixing chamber in a tangential direction and the division of the streams before introduction into the mixing chamber provides a homogeneous mixture of the fuel gas and the air and causes complete combustion of the fuel gas mixture consisting of a mixture of blast furnace gas and coke oven or natural gas.

In the preferred embodiment of the invention, fuel gas and air are tangentially introduced into the mixing chamber through the superimposed channels in different streams. By dividing the fuel gas and the air streams into a number of superimposed streams, good mixing of the fuel gas and the air is obtained upon entering of the gases into the mixing chamber, such mixing being even more intense by providing different speeds for the fuel gas and the air entering the mixing chamber. Complete admixing of the two gases occurs in the mixing chamber wherethe gases are rotated with great turbulence due to the fact that the superimposed streams enter into the mixing chamber, of circular cross section, along a tangential path. The mixture obtained in this manner is so complete that the gases begin to burn shortly before leaving the mixing chamber and the combustion is so intense that even under full load conditions, complete combustion is already obtained at half the height of the combustion chamber above the mixing chamber with only little excess air.

The invention will become more readily apparent from the following description of an embodiment thereof shown in the accompanying drawings, in which:

FIG. I is a vertical sectional view of a burner formed in accordance with the teachings of the invention and taken substantially along line II of FIG. 2;

FIG. 2 is a cross-sectional view of the burner of the invention taken substantially along line II -II of FIG. 1;

FIG. 3 is a cross-sectional view of the gas admission channels of the burner taken substantially along line IIIIII of FIG. 1; and

FIG. 4 is an elevational plan view of the exit end of the gas admission channels as seen from the mixing chamber of the burner (i.e., along line IVIV of FIG. 1).

With reference now to the drawings, and particularly to FIG. I, there is shown a generally cylindrical mixing chamber l for air and combustible gas. The wall of the cylindrical mixing chamber 1 is built from firebricks which, at the upper end of the mixing chamber 1, are displaced inwardly to form a conical throat 2. The lower end of the mixing chamber is closed by a bottom 3.

Near the bottom of the chamber 1 are three superimposed channels 4, 5 and 6 formed from refractory material. The lower channel 4 and the upper channel 5 are fuel gas admission channels; whereas the intermediate channel 6 is an air admission channel. As can be seen from FIG. 4, the channels have substantially rectangular cross sections at the point where they intersect the cylindrical mixing chamber 1, the width of the three channels being the same. At its entrance end, the air channel 6 is of circular cross-sectional configuration and has a short feed pipe 7 connecting it to an air admission valve, not shown. The feed pipe 7 is surrounded by a conical hood 8 such that between the feed pipe 7 and the hood 8 an annular space is formed through which the fuel gas is admitted to the fuel gas channels 4 and 5. As will be understood, there can be provided different means for admitting the gases to the admission channels. Furthermore, instead of using two gas channels and a single, central air channel, only a single gas and single air channel can be used, one above the other as was explained above.

The relative positions of the combustion chamber 9, the mixing chamber 1 and the gas admission channels 4, and 6 can be seen clearly from FIGS. 1 and 2. In FIG. 2, it will be noted that the air channel 6, as well as the gas channels 4 and 5 below and above it, intersect the mixing chamber 1 tangentially. Therefore, the gases, as they enter the mixing chamber 1, are imparted a rotational motion as indicated by the arrow 1 1 in FIG. 2. This causes the speed of the gases to be higher near the walls of the combustion chamber than in the center thereof. Depending upon various conditions, the gas speed at the center of the mixing chamber may be zero or may actually have a reverse flow. In order to impede the rotational flow at the walls of the mixing chamber 1, it is provided at its upper end with the conical throat 2. This causes a certain amount of the rotating gases near the walls of the combustion chamber to move toward the center where complete admixing occurs. After complete admixing of the gases in this manner, they pass upwardly through the throat 2 and thence into the combustion chamber where they burn. The products of combustion then pass upwardly to the dome of a blast furnace stove 10, for example, and then downwardly into space 12 (FIG. 2) filled with checkerbricks which are heated by the products of combustion preparatory to a reverse flow of air through the checkerbricks and the combustion chamber. The hot blast of air, after passing through the checkerbricks and combustion chamber, may then be conducted to a blast furnace through conduit 13, for example, shown in FIG. 2. As mentioned above, exceptionally good mixing of the air and fuel gas streams are achieved when their velocities are different. Either the air or fuel stream can be of higher velocity than the other.

Actual experiments have shown that the temperatures achieved in the burner are adjustable within the range of l :5. The temperatures at the center of the mixing chamber during the experiments were 600C for the smallest gas flow and about 150C for the largest gas flow. This, of course, is due to the fact that higher gas flows produce a certain cooling effect within the mixing chamber.

Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. The combination characterized by an air-gaseous fuel mixing chamber for supplying an air-gaseous mixture to a combustion chamber that in turn discharges a blast of heated air at a temperature of 1,200C and greater to a blast furnace, said combination comprising:

a combustion chamber receiving an air-gaseous mixture for combustion therein and upward discharge of a combustion product including a blast of heated air to said blast furnace;

substantially cylindrical air-gaseous fuel mixing chamber extending along a vertical axis with the upper end thereof communicating with one end of said combustion chamber, the upper end of said mixing chamber including a conical throat of reduced diameter at its upper end where the throat is connected to and discharges an air-gaseous fuel mixture to said combustion chamber, said conical throat serving to cause rotating gases at the walls of the mixing chamber to move inwardly toward the center thereof;

refractory material for forming said mixing chamber;

and

at least two horizontally-extending channels formed from refractory material and separated from each other at the lower end of said mixing chamber, said channels intersecting said cylindrical mixing chamber tangentially in a manner such that one of said channels conducts a gaseous fuel into said mixing chamber for mixture therein with air conducted into said mixing chamber by the other of said channels.

2. The air-gaseous fuel mixing device as claimed in claim 1, wherein said horizontally-extending channels are superimposed.

3. The air-gaseous fuel mixing device as claimed in claim 2, wherein there are three superimposed horizontally-extending channels, the intermediate channels serving for the admission of air to the mixing chamber and the upper and lower channels serving for the admission of fuel gas to the mixing chamber.

4. The air-gaseous fuel mixing device as claimed in claim 3, wherein the horizontally-extending channels have substantially rectangular cross sections and are of equal width at the point where they intersect the mixing chamber. 

1. The combination characterized by an air-gaseous fuel mixing chamber for supplying an air-gaseous mixture to a combustion chamber that in turn discharges a blast of heated air at a temperature of 1,200*C and greater to a blast furnace, said combination comprising: a combustion chamber receiving an air-gaseous mixture for combustion therein and upward discharge of a combustion product including a blast of heated air to said blast furnace; a substantially cylindrical air-gaseous fuel mixing chamber extending along a vertical axis with the upper end thereof communicating with one end of said combustion chamber, the upper end of said mixing chamber including a conical throat of reduced diameter at its upper end where the throat is connected to and discharges an air-gaseous fuel mixture to said combustion chamber, said conical throat serving to cause rotating gases at the walls of the mixing chamber to move inwardly toward the center thereof; refractory material for forming said mixing chamber; and at least two horizontally-Extending channels formed from refractory material and separated from each other at the lower end of said mixing chamber, said channels intersecting said cylindrical mixing chamber tangentially in a manner such that one of said channels conducts a gaseous fuel into said mixing chamber for mixture therein with air conducted into said mixing chamber by the other of said channels.
 2. The air-gaseous fuel mixing device as claimed in claim 1, wherein said horizontally-extending channels are superimposed.
 3. The air-gaseous fuel mixing device as claimed in claim 2, wherein there are three superimposed horizontally-extending channels, the intermediate channels serving for the admission of air to the mixing chamber and the upper and lower channels serving for the admission of fuel gas to the mixing chamber.
 4. The air-gaseous fuel mixing device as claimed in claim 3, wherein the horizontally-extending channels have substantially rectangular cross sections and are of equal width at the point where they intersect the mixing chamber. 